Estimation of cardiac preload changes by systolic pressure variation in pigs undergoing pneumoperitoneum

BACKGROUND: Variations in systolic pressure arterial waveform (SPV) and its component have been shown to be a reasonable indicator of left ventricular preload. Creation of a pneumoperitoneum (PMOP) by insufflation of CO2 increases intrathoracic pressure, leading to overestimation of preload as assessed by pressure methods. The purpose of this study was to compare SPV with other standard methods in anaesthetized pigs. METHODS: We measured SPV and its DeltaDown component (deltaDown), pulmonary artery occlusion pressure (PAOP) and left ventricular short-axis cross-sectional area using transthoracic echocardiography (TTE) in 7 pigs, at baseline, after 12 mmHg PMOP and after an intravascular load with 10 ml/kg hydroxylethylstarch (HES). RESULTS: PMOP increased SPV from 12.9+/-4.9 to 16.9+/-5.5 mmHg (P<0.05) and decreased pulmonary compliance, with no change in PAOP or end-diastolic area assesssed by TTE. Intravascular volume loading significantly decreased SPV from 16.9+/-5.5 to 11.2+/-4.9 mmHg and deltaDown from 9.9+/-7.1 to 5.2+/-4.5 (P<0.05), and increased PAOP and end-diastolic area. Significant correlation between changes in deltaDown and EDA was noted following HES (r=0.78, P<0.05). CONCLUSION: In anaesthetized pigs, the creation of a PMOP alters SPV, likely by decreasing lung compliance. Once PMOP is established, changes in cardiac preload could be estimated by SPV analysis.     

Hemodynamics during liver transplantation

Assessing the optimal volemia in the perioperative course of liver transplantation is a challenge for the anesthesiologist. Traditional estimates of intravascular volume status, such as pulmonary artery occlusion pressure (PAOP), have been widely shown to poorly correlate with changes in cardiac output among critically ill patients. Hence, there has been recent interest in alternative, catheter-related, bedside device volume estimates using thermodilution. Continuous end diastolic volume (CEDVI) showed better correlations with cardiac performance than cardiac filling pressures in studies performed in critically ill patients. When compared with conventional pressure-derived data, preload monitoring estimated as intrathoracic blood volume index (ITBVI) with the PiCCO system based on an integrated transpulmonary thermodilution technique better reflected left ventricular filling both in critically ill patients and those who underwent liver transplantation. Moreover, in liver transplantation, the use of transoesophageal echocardiography (TEE) has been increasing for it provides rapid visualization of the dimension and function of heart chambers as well as the left ventricular end diastolic area index (EDAI) that seem to correlate with graded acute hypovolemia, although its validity as on preload index is still under discussion.     

Systolic pressure variation in hemodynamic monitoring after severe blast injury.

Fluid management in patients following blast injury is a major challenge. Fluid overload can exacerbate pulmonary dysfunction, whereas suboptimal resuscitation may exacerbate tissue damage. In three patients, we compared three methods of assessing volume status: central venous (CVP) and pulmonary artery occlusion (PAOP) pressures, left ventricular end-diastolic area (LVEDA) as measured by transesophageal echocardiography, and systolic pressure variation (SPV) of arterial blood pressure. All three patients were mechanically ventilated with high airway pressures (positive end-expiratory pressure 13 to 15 cm H2O, pressure control ventilation of 25 to 34 cm H2O, and I:E 2:1). Central venous pressure and PAOP were elevated in two of the patients (CVP 14 and 18 mmHg, PAOP 25 and 17 mmHg), and were within normal limits in the third (CVP 5 mmHg, PAOP 6 mmHg). Transesophageal echocardiography was performed in two patients and suggested a diagnosis of hypovolemia (LVEDA 2.3 and 2.7 cm2, shortening fraction 52% and 40%). Systolic pressure variation was elevated in all three patients (15 mmHg, 15 mmHg, and 20 mmHg), with very prominent dDown (23, 40, and 30 mmHg) and negative dUp components, thus corroborating the diagnosis of hypovolemia. Thus, in patients who are mechanically ventilated with high airway pressures, SPV may be a helpful tool in the diagnosis of hypovolemia.     

Kardiale Vorlast und zentraler Venendruck

The force of cardiac contraction is strongly influenced by myocardial fibre length at the beginning of systole. Because the length of cardiac sarcomers and muscle fibres primarily depends on the end-diastolic ventricular volume, filling pressures a priori can only act as indirect parameters of cardiac preload. Central venous pressure (CVP) gives information on right ventricular end-diastolic pressure, which parallels changes in left ventricular end-diastolic pressure as long as ventricular function is not impaired. Since the pressure-volume relationship of cardiac ventricles is not linear and shows great variability, filling of the ventricles cannot be directly derived from end-diastolic pressure. Further limitations of CVP as a surrogate variable of preload are caused by the influence of intrathoracic and intra-abdominal pressures. A valid parameter of preload should describe the relationship between preload and stroke volume as given by the Frank-Starling law. Furthermore, estimates of cardiac preload should enable prediction of fluid responsiveness. Many studies have demonstrated that under clinical conditions CVP cannot meet these demands and thus does not appear to be a useful predictor of cardiac preload. Variables which more directly represent end-diastolic ventricular volume (e.g. intrathoracic blood volume or end-diastolic ventricular area) offer a higher validity as estimates of cardiac preload. Furthermore, dynamic parameters of ventricular preload, such as pulse pressure variation or stroke volume variation, seem to be more predictive of volume responsiveness in ventilated patients than CVP. These limitations, however, do not impair the importance of CVP as the downstream pressure of the systemic venous system.     

Trendelenburg positioning after cardiac surgery: effects on intrathoracic blood volume index and cardiac performance

BACKGROUND AND OBJECTIVE: The efficacy of the Trendelenburg position, a common first step to treat suspected hypovolaemia, remains controversial. We evaluated its haemodynamic effects on cardiac preload and performance in patients after cardiac surgery. METHODS: Twelve patients undergoing mechanical ventilation of the lungs who demonstrated left ventricular 'kissing papillary muscles' by transoesophageal echocardiography, thus suggesting hypovolaemia, were positioned 30 degrees head down for 15 min immediately after cardiac surgery. Cardiac output by thermodilution, central venous pressure, pulmonary artery occlusion pressure, left ventricular end-diastolic area by transoesophageal echocardiography and intrathoracic blood volume by thermo- and dye dilution were determined before, during and after this Trendelenburg manoeuvre. RESULTS: Trendelenburg's manoeuvre was associated with increases in central venous pressure (9 +/- 2 to 12 +/- 3 mmHg) and pulmonary artery occlusion pressure (8 +/- 2 to 11 +/- 3 mmHg). The intrathoracic blood volume index increased slightly (dye dilution from 836 +/- 129 to 872 +/- 112 mL m(-2); thermodilution from 823 +/- 129 to 850 +/- 131 mL m(-2)) as did the left ventricular end-diastolic area index (7.5 +/- 2.1 to 8.1 +/- 1.7 cm2 m(-2)), whereas mean arterial pressure and the cardiac index did not change significantly. After supine repositioning, the cardiac index decreased significantly below baseline (3.0 +/- 0.6 versus 3.5 +/- 0.8 L min(-1) m(-2)) as did mean arterial pressure (76 +/- 12 versus 85 +/- 11 mmHg), central venous pressure (8 +/- 2 mmHg) and pulmonary artery occlusion pressure (6 +/- 4 mmHg). The intrathoracic blood volume index and left ventricular end-diastolic area index did not differ significantly from baseline. CONCLUSIONS: Trendelenburg's manoeuvre caused only a slight increase of preload volume, despite marked increases in cardiac-filling pressures, without significantly improving cardiac performance.     

Prognostic value of biventricular function in hypotensive patients after cardiac surgery as assessed by transesophageal echocardiography.

In patients after cardiac surgery, hypotension, defined as a mean arterial pressure less than 65 mmHg despite adequate filling pressures and positive inotropic medication, poses a problem. In addition, it is often difficult to determine whether these patients have suffered irreversible myocardial injury or if they are likely to recover. In this study, left and right ventricular function, as assessed by transesophageal echocardiography (TEE), was related to mortality both (1) quantitatively, using fractional area change (FAC), and (2) qualitatively, using a segmental wall motion analysis, which assigned a score to myocardial wall segments, in order to determine whether this technique can be used to predict survival. Mortality rate was very high in patients with biventricular and especially right ventricular failure (FAC less than 35%). Left and right ventricular wall motion abnormality indices were significantly better in survivors compared to nonsurvivors, but no distinct cut-off value could be determined. A wall motion index derived from only 6 segments at the mid-papillary muscle level was found to be as reliable as one based on 16 segments of the entire left ventricle. Thus, TEE provided information about the degree of left and right ventricular dysfunction by using a single cross-section at the papillary muscle level. It identified patients at high risk of death, ie, those with compromised right and biventricular function.     

Transesophageal Atrial Pacing in Anesthetized Patients with Coronary Artery Disease: Hemodynamic Benefits Versus Risk of Myocardial Ischemia

Background: Transesophageal atrial pacing (TEAP) provides prompt and precise control of heart rate and improves hemodynamics in anesthetized patients with bradycardia and hypotension. The authors' purpose in this study was to examine the hemodynamic benefits of TEAP versus the risk of myocardial ischemia in patients about to undergo coronary artery bypass surgery.

Methods: Hemodynamics, ventricular filling pressures, mixed venous oxygen saturation, and end-diastolic, end-systolic, and fractional area change of the left ventricle, determined by transesophageal echocardiography (TEE), were measured after anesthesia induction with 30 micro gram/kg fentanyl and at incremental TEAP rates of 65, 70, 80, and 90 beats/min (bpm) in 40 adult patients. Monitoring for myocardial ischemia was accomplished with 12-lead electrocardiograms and biplane TEE assessment of left ventricular regional wall motion. Hemodynamics, electrocardiograms, and TEE measurements at each TEAP rate were compared with baseline awake measurements (except TEE) and with measurements obtained after anesthesia induction before TEAP.

Results: Sinus bradycardia occurred in 15 patients after anesthesia induction and was associated with a hypotensive response and a decrease in cardiac output in 10 patients. In these patients, TEAP restored diastolic blood pressure and cardiac output to baseline values at TEAP rates of 65 and 80 bpm, respectively. Stroke volume was similar to baseline measurements after anesthesia induction and at TEAP rates of 65, 70, and 80 bpm, but was significantly reduced from baseline at TEAP 90 bpm. Myocardial ischemia was detected in 7 and 5 patients at a TEAP rate of 80 and 90 bpm, respectively.     

Transesophageal echocardiographic dimensional analysis of four cardiac chambers during positive end-expiratory pressure

The authors examined the effects of positive end-expiratory pressure (PEEP) on cardiac function by dimensional analysis of the four heart chambers using M-mode transesophageal echocardiography (TEE). The accuracy of cardiac output (CO) calculated from TEE was confirmed by its close correlation (r = 0.97) with CO, determined by the thermodilution technique. The reliability of TEE also was confirmed by excellent correlation (r = 0.95) between left ventricular end-diastolic (LVEDD) and end-systolic (LVESD) dimensions measured by the two-dimensional precordial echocardiography and those by TEE. With 10 cmH2O PEEP LVEDD decreased from its level during zero end-expiratory pressure (ZEEP), and the calculated stroke volume also decreased. These decreases were greater during 15 cmH2O PEEP, where heart rate increased slightly but significantly. Ejection fraction (EF) and fractional shortening (FS), as a whole, did not change significantly. Mean velocity of circumferential fiber shortening (mean Vcf) significantly increased and LVESD significantly decreased with PEEP. Although systolic blood pressure (SBP) significantly decreased, the (SBP-PEEP value)/LVESD ratio was not changed with PEEP. Such measures of left ventricular systolic function as EF, FS, mean Vcf, and (SBP-PEEP value)/LVESD were not decreased. Right ventricular end-diastolic dimension decreased with PEEP. Right atrial end-diastolic dimension began to decrease immediately after PEEP was initiated, whereas left atrial end-diastolic dimension began to decrease a few seconds later, suggesting that left ventricular preload decreased as a result of a decrease in right ventricular preload. The authors therefore conclude that CO was decreased as a result of the decrease in right and left ventricular preloads.     

Assessment of volume responsiveness in mechanically ventilated patients

Monitoring and management of intravascular volume status is of crucial importance in critically ill patients. Hypovolemia, induced by hemorrhage or pathologic fluid shifts in the presence of systemic inflammation, is frequently the cause for hemodynamic instability and hypotension. This deficit of central blood volume leads to a reduction in biventricular cardiac preload. With respect to the Frank-Starling mechanism, this causes an alteration in left ventricular stroke volume. If this reduction in stroke volume cannot be compensated by an increase in heart rate, this finally results in a decline of cardiac output. In this clinical situation fluid loading is the treatment of choice. However, insufficient peripheral vascular resistance and thus reduced cardiac afterload as well as impaired myocardial contractility also have to be taken in account to be causative for hypotension. Potential hazards of fluid loading specifically in the latter situation include pulmonary edema, worsening of pulmonary gas exchange and myocardial failure. Thus, prediction of fluid responsiveness, i.e. the prediction of the hemodynamic response to fluid loading is of utmost importance in critically ill patients. Several conventional parameters of systemic hemodynamic monitoring such as the cardiac filling pressures CVP and PAOP, the estimation of the left ventricular end-diastolic area (LVEDA) by echocardiography and measurement of central blood volumes as the right-ventricular end-diastolic volume (RVEDV) or the global end-diastolic volume (GEDV) by thermodilution are frequently used for preload monitoring. Further, functional preload parameters such as the left ventricular stroke volume variation (SW), describing the specific interactions of the heart and the lungs under mechanical ventilation, have been recently proposed to be useful for predicting fluid responsiveness. Thus, it is the aim of the present article to analyze these different concepts of hemodynamic monitoring regarding their usefulness and clinical applicability to predict fluid responsiveness at the bedside.     

Monitoring intravascular volumes for postoperative volume therapy

BACKGROUND AND OBJECTIVE: The feasibility of monitoring measured intravascular volumes and the cardiac filling pressures were compared to reflect the optimal volume status of postoperative patients. METHODS: In a prospective clinical study, 14 hypovolaemic adult patients were included after cardiac surgery. All patients received 1,000 mL hydroxyethyl starch after meeting the authors' criteria for hypovolaemia. Pressures were measured by use of a pulmonary artery catheter and volumes were determined by double-indicator dilution technique. RESULTS: Stroke volume index (SVI), central venous pressure (CVP), pulmonary artery occlusion pressure (PAOP), intrathoracic blood volume index (ITBVI) and total circulating blood volume (TBVIcirc) increased significantlyaftervolumeloading(30.7 +/- 9.8 to 41.7 +/- 9.6 mLm(-2), 4.9 +/- 1.7 to 9.1 +/- 2.3mmHg, 6.6 +/- 1.3 to 10.6 +/- 1.9 mmHg, 858 +/- 255 to 965 +/- 163 mLm(-2), and 1,806 +/- 502 to 2,110 +/- 537 mLm(-2), respectively). During the subsequent 1 h steady-state period, CVP and PAOP decreased significantly (9.1 +/- 2.2 to 7.4 +/- 2.2 mmHg and 10.6 +/- 1.9 to 9.2 +/- 2.0 mmHg, respectively), whereas SVI and intravascular volumes remained unchanged. The changes of CVP and PAOP did not correlate with changes in stroke volume during volume loading (r2 = 0.06 and 0.03, respectively) and during steady-state (r2 = 0.17 and 0.00 respectively). On the other hand, a significant correlation was found between changes of the intrathoracic blood volume and changes in stroke volume during the volume loading (r2 = 0.67) and also during the steady-state phase (r2 = 0.83). CONCLUSIONS: Intrathoracic blood volume reflects more accurately the preload dependency of cardiac output in postoperative patients than left/right-sided cardiac filling pressures.     

Poor correlation between pulmonary arterial wedge pressure and left ventricular end-diastolic volume after coronary artery bypass graft surgery

The authors studied 12 surgical patients in the intensive care unit post coronary artery bypass graft surgery and ten nonsurgical patients in the coronary care unit with chronic heart failure to determine the usefulness of the pulmonary arterial wedge pressure as an indicator of left ventricular preload. Left ventricular end diastolic volume was derived from concomitant determination of ejection fraction (gated blood pool scintigraphy) and stroke volume (determined from thermodilution cardiac output). In the nonsurgical patients, there was a significant correlation between changes in pulmonary arterial wedge pressure and left ventricular end-diastolic volume (P less than 0.05, r = 0.57). In the 12 patients studied during the first few hours after surgery, there was a poor correlation between changes in pulmonary wedge pressure (range = 4-32 mmHg) and left ventricular end-diastolic volume (range = 25-119 ml/m2), and a poor correlation between pulmonary arterial wedge pressures and stroke work index. In contrast, there was a good correlation between left ventricular end-diastolic volume and stroke work index. The poor correlation between the pulmonary arterial wedge pressure and left ventricular end-diastolic volume was not explained by changes in systemic or pulmonary vascular resistance. The altered ventricular pressure-volume relationship may reflect acute changes in ventricular compliance in the first few hours following coronary artery bypass graft surgery. While measurement of pulmonary arterial wedge pressure remains valuable in clinical management to avoid pulmonary edema, it cannot reliably be used as an index of left ventricular preload while attempting to optimize stroke volume in patients immediately following coronary artery bypass graft surgery.     

Left ventricular reshaping: effects on the pressure-volume relationship

OBJECTIVE: We tested whether the CardioClasp device (CardioClasp, Inc, Cincinnati, Ohio), a non-blood contact device, would improve left ventricular contractility by acutely reshaping the left ventricle and reducing left ventricular wall stress. METHODS: In dogs (n = 6) 4 weeks of ventricular pacing (210-240 ppm) induced severe heart failure. Left ventricular function was evaluated before and after placement of the CardioClasp device, which uses 2 indenting bars to reshape the left ventricle. Hemodynamics, echocardiography, and Sonometrics crystals dimension (Sonometrics Corporation, London, Ontario, Canada) were measured at steady state and during inferior vena caval occlusion. RESULTS: The CardioClasp device decreased the left ventricular end-diastolic anterior-posterior dimension by 22.8% +/- 1.9%, decreased left ventricular wall stress from 97.3 +/- 22.8 to 67.2 +/- 7.7 g/cm(2) (P =.003), and increased the fractional area of contraction from 21.3% +/- 10.5% to 31.3% +/- 18.1% (P =.002). The clasp did not alter left ventricular end-diastolic pressure, left ventricular pressure, left ventricular dP/dt, or cardiac output. With the CardioClasp device, the slope of the end-systolic pressure-volume relationship was increased from 1.87 +/- 0.47 to 3.22 +/- 1.55 mm Hg/mL (P =.02), the slope of preload recruitable stroke work versus end-diastolic volume was increased from 28.4 +/- 11.0 to 44.1 +/- 23.5 mm Hg (P =.02), and the slope of maximum dP/dt versus end-diastolic volume was increased from 10.6 +/- 4.6 to 18.6 +/- 7.4 mm Hg x s(-1) x mL(-1) (P =.01). The CardioClasp device increased the slope of the end-systolic pressure-volume relationship by 68.0% +/- 21.7%, the slope of preload recruitable stroke work versus end-diastolic volume by 50.7% +/- 18.1%, and the slope of maximum dP/dt versus end-diastolic volume by 85.7% +/- 28.9%. CONCLUSIONS: The CardioClasp device decreased left ventricular wall stress and increased the fractional area of contraction by reshaping the left ventricle. The CardioClasp device was able to maintain cardiac output and arterial pressure. The clasp increased global left ventricular contractility by increasing the slope of the end-systolic pressure-volume relationship, the slope of preload recruitable stroke work versus end-diastolic volume, and the slope of maximum dP/dt versus end-diastolic volume. In patients with heart failure, the CardioClasp device might be effective for clinical application.     

Atrial fibrillation after coronary artery bypass graft surgery is unrelated to cardiac abnormalities detected by transesophageal echocardiography.

Atrial fibrillation is a common complication of coronary artery bypass graft (CABG) surgery that is associated with adverse patient outcomes. We evaluated whether preexisting abnormalities of cardiac structure or function detected with transesophageal echocardiography (TEE) are prevalent in patients later developing atrial fibrillation after CABG surgery. TEE imaging was performed after induction of general anesthesia, but before primary CABG surgery, in 62 consecutive patients without cardiac valvular disease or preexisting atrial fibrillation. Measurements included left atrial diameter, left ventricular wall thickness, left ventricular end-systolic and end-diastolic dimensions and fractional area change. Pulsed-wave Doppler measurements of pulmonary venous and trans-mitral blood flow velocity were obtained. Continuous monitoring with telemetry electrocardiography for the development of atrial fibrillation was performed. Eighteen patients (29%) developed postoperative atrial fibrillation. There were no significant differences in left atrial or left ventricular TEE variables or pulsed-wave Doppler pulmonary venous flow measurements between patients with and without postoperative atrial fibrillation. After adjusting for age and duration of aortic cross-clamping, there were no differences in the transmitral Doppler diastolic filling variables between these same groups. These data suggest that atrial fibrillation commonly occurs after CABG surgery in the absence of atrial enlargement or Doppler-derived cardiac functional abnormalities. The data imply that the use of TEE immediately before surgery would be an insensitive means for routine identification of patients susceptible to this arrhythmia. Implications: Transesophageal echocardiography performed immediately before coronary artery bypass graft (CABG) surgery is not useful for prediction of susceptibility to develop atrial fibrillation postoperatively. Postoperative atrial fibrillation commonly occurs after CABG surgery in the absence of preoperative atrial enlargement or Doppler derived functional abnormalities.     

Hemodynamic effects of portal triad clamping with and without pneumoperitoneum: an echocardiographic study

The decrease of cardiac index observed during portal triad clamping (PTC) with and without pneumoperitoneum has been studied only with right heart catheterization. To better understand this decrease of cardiac index, we investigated the balance between the adequacy of preload and the ability of the heart to pump against an increased afterload, by using transesophageal echocardiography. Ten patients with PTC performed during laparoscopy and 10 with PTC performed during laparotomy were studied. Five minutes after PTC, the stroke volume, the left ventricular (LV) fractional area change (FAC), and the LV end-systolic wall stress (LVESWS) were measured as the conventional hemodynamic variables. Regional wall motion abnormalities (RWMA) were also recorded. In the laparotomy group, LV end-diastolic area decreased, and LVESWS did not increase significantly. FAC remained stable, and one patient developed RWMA. In the laparoscopic group, LV end-diastolic area remained stable, and LVESWS increased. FAC decreased significantly, and five patients developed RWMA. A decrease in preload was the main important change in the laparotomy group, and in the laparoscopic group a decrease in LV function was demonstrated that was likely a consequence of decreased LV preload and increased LV afterload. However, these did not necessitate stopping the procedure or releasing PTC in these study patients without cardiac disease.     

The role of transesophageal echocardiography in optimizing resuscitation in acutely injured patients

BACKGROUND: The goal of resuscitation is to correct the mismatch between oxygen delivery and that of cellular demands. The pulmonary artery catheter (PAC) is frequently used to gauge the adequacy of resuscitation and guide therapy based on ventricular filling pressures. Transesophageal echocardiography (TEE) has emerged as a potential tool in assessing adequacy of acute hemodynamic resuscitation. The purpose of this study was to evaluate the role of TEE in assessing preload during ongoing volume resuscitation in trauma patients. METHODS: A retrospective review was conducted of acutely injured patients undergoing TEE during resuscitation from hemorrhagic shock from January 2002 to 2004 at a Level I trauma center. The indication for TEE was persistent hemodynamic instability in the absence of ongoing surgical hemorrhage. Variables included hemodynamic and PAC parameters, pre-TEE resuscitation volume, and vasopressor requirements. The impact of TEE findings on therapeutic decisions was evaluated. RESULTS: Twenty-five patients underwent TEE, 18 (72%) had an indwelling PAC with a mean pulmonary artery occlusion pressure of 19.3 mm Hg (range, 12-29 mm Hg) and mean cardiac index of 2.9 L/min/m2 (range, 1.6-4.6 L/min/m2). Twelve patients (48%) were receiving inotropes and/or vasopressors for hypotension at the time of TEE. Resuscitation volume within 6 hours before TEE included a mean of 6.5 L of crystalloid and 12.2 units of blood products (packed red blood cells, fresh frozen plasma, and platelets). TEE revealed left ventricular hypovolemia in 13 patients (52%) and altered therapy in 16 patients (64%), including additional volume (n = 13), addition of an inotrope (n = 4), and addition of a vasodilator (n = 1) in one patient with ventricular overdistention. Comparison of the abnormal and normal TEE groups revealed that only cardiac index was significantly different (2.6 L/min/m2 in the abnormal group vs. 3.9 L/min/m2 in the normal group; p = 0.005). Significant mitral valve regurgitation leading to valve replacement was identified in one patient. No clinically relevant pericardial effusion was identified. CONCLUSION: TEE altered resuscitation management in almost two thirds of patients. Many patients with "acceptable" pulmonary artery occlusion pressure parameters may in fact have inadequate left ventricular filling. In addition, TEE offers the advantage of direct assessment of cardiac valve competency, myocardial wall contractility, and pericardial fluid.     

Assessment of cardiac preload by indicator dilution and transoesophageal echocardiography.

BACKGROUND AND OBJECTIVE: Assessment of cardiac preload is of major importance in the management of critically ill patients. Echocardiographic determined left ventricular end-diastolic area and indicator dilution derived intrathoracic blood volume are used as surrogates for cardiac preload. However, no controlled comparison studies on the relationship between induced changes in end-diastolic area and intrathoracic blood volume and concomitant changes in stroke volume index are available. METHODS: The effects of a change in body position on these variables were investigated in 10 anaesthetized patients. RESULTS: Intrathoracic blood volume and end-diastolic area decreased by 18 +/- 11% and 27 +/- 13% respectively. Stroke volume index concomitantly decreased by 19 +/- 11%. Correlation analysis revealed a close relation between stroke volume index and intrathoracic blood volume (r=0.75) and end-diastolic area (r=0.76). CONCLUSIONS: Within the observed range of data, intrathoracic blood volume and end-diastolic area are equivalent indices of cardiac preload.     

A Comparison of Left Ventricular Performance Indices Measured by Transesophageal Echocardiography with Automated Border Detection

Background: Automated border detection (ABD) allows semiautomated measurement of left ventricular (LV) areas. They can be combined with left ventricular pressure signals to generate pressure-area loops and pressure-dimension indices of contractility. This study compared conventional indices of ventricular performance (fractional area change [FAC] and circumferential fiber shortening [Vcfc]) with pressure-dimension indices of contractility. A secondary aim was to compare the effects of volatile anesthetics on the indices.

Methods: Using transesophageal echocardiography with automated border detection, FAC and Vcfc were obtained in 23 patients after cardiopulmonary bypass. Left ventricular pressures were obtained with a left ventricular catheter. Preload reduction by inferior vena caval occlusion was used to obtain end-systolic elastance (Ees), preload recruitable stroke force (PRSF), and dP/dtmax [middle dot] EDA-1 (EDA = end-diastolic area). In 11 patients, the measurements were repeated at 1 end-tidal minimum alveolar concentration of halothane or isoflurane. The results are expressed as mean +/- SD.

Results: After cardiopulmonary bypass, FAC was 31.1 +/- 7.9%, Vcfc was 0.6 +/- 0.2 circ [middle dot] s-1, Ees was 25.8 +/- 11.6 mmHg [middle dot] cm-2, PRSF was 60.8 +/- 26.6 mmHg, and dP/dtmax [middle dot] -EDA-1 was 245 +/- 123.4 mmHg [middle dot] s-1 [middle dot] cm-2. At 1 minimum alveolar concentration of a volatile anesthetic agent, FAC, Vcfc, and dP/dtmax [middle dot] EDA-1 remained unchanged. Significant decreases in Ees (19%) and PRSF (28%) were observed.     

Beat-to-beat Augmentation of Left Ventricular Function by Intraaortic Counterpulsation

Background: Measuring the effects of intraaortic balloon counterpulsation (IABP) in single cardiac beats may permit an improved understanding of the physiologic mechanisms by which IABP improves the circulation. The objective of the study was to use transesophageal echocardiography in combination with hemodynamic measurements to test the hypothesis that IABP improves global left ventricular systolic function selectively in the IABP-augmented cardiac beats by acutely decreasing left ventricular afterload.

Methods: Twenty-seven studies in which the IABP-to-R wave trigger ratio was serially changed from 1:1, 1:2, 1:4, 0:1 (IABP off) and back to 1:1 were performed in 20 anesthetized cardiac surgical patients during IABP support. Left ventricular short-axis end-diastolic cross-sectional area, end-systolic area, mean end-systolic wall thickness, and ejection time were measured by transesophageal echocardiography at the midpapillary muscle level. Aortic pressure was measured simultaneously from the central lumen of the intraaortic balloon catheter. These measurements were used to calculate the fractional area change, end-systolic meridional wall stress, and heart rate-corrected velocity of circumferential fiber shortening. The echocardiographic and hemodynamic parameters of left ventricular preload, afterload, and systolic function immediately after balloon deflation (IABP-augmented cardiac beats) were compared to the parameters measured during nonaugmented cardiac beats to determine the beat-to-beat effects of IABP on left ventricular function.

Results: IABP-augmented cardiac beats had a decreased systolic arterial pressure and end-systolic meridional wall stress and increased diastolic blood pressure, fractional area change, and velocity of circumferential fiber shortening compared to the nonaugmented cardiac beats. IABP did not cause significant beat-to-beat changes in heart rate, pulmonary artery diastolic pressure, or central venous pressure. The improvement in left ventricular systolic function associated with IABP-augmented cardiac beats correlated with the decrease in end-systolic meridional wall stress for that cardiac beat.     

Transesophageal echocardiography during coronary bypass surgery

Transesophageal two-dimensional echocardiography (TEE) was evaluated in 14 patients who underwent coronary bypass surgery. The TEE transducer was positioned to view the left ventricular short axis at the level of the papillary muscle. Global left ventricular function was assessed by measuring left ventricular end-diastolic and end-systolic area and computing the fractional area change (FAC). Regional left ventricular function was analyzed after dividing the short axis view of the left ventricle into four anatomic segments. The mean FAC was 48% after intubation, 48% after skin incision, 47% after sternotomy, and 51% after pericardiotomy. The mean FAC increased significantly to 55% 0 to 30 minutes after cardiopulmonary bypass, and was 53% at the end of the operation. In 5 patients, FAC decreased and regional wall motion abnormalities appeared around sternotomy. These abnormalities was considered due to transient myocardial ischemia. In 7 patients, a paradoxical motion of the ventricular septum occurred at closing of the sternum. TEE was performed without complication and found to be a good method for assessing global and regional left ventricular function.     

Effect of acutely increased left ventricular afterload on work output from the right ventricle in conscious dogs

OBJECTIVE: To determine the effect of acute increments in left ventricular afterload on the stroke work output of the right ventricle in vivo. METHODS: After pharmacologic attenuation of autonomic reflexes, left and right ventricular pressure-volume data were obtained in 9 conscious dogs during vena caval occlusions performed before and during aortic constriction. RESULTS: The relationship between right ventricular stroke work and end-diastolic volume during vena caval occlusion was highly linear (r = 0.97 +/- 0.02), but the slope decreased by 20% +/- 13% during aortic constriction sufficient to increase left ventricular mean ejection pressure by 25% +/- 14% (P <.05). The volume-axis intercept remained constant. Similarly, the slope of the linear relationship between right ventricular free wall regional segment work and end-diastolic segment length declined by 22% +/- 10% during aortic constriction (P <.05), without significant change in the length-axis intercept. The reduction in both global and regional right ventricular stroke work at any given preload with increased left ventricular afterload was due entirely to decreased right ventricular stroke volume and free wall shortening, because right ventricular mean ejection pressure was unchanged. Additional experiments were performed in 5 open-chest dogs to produce a greater reduction in left ventricular free wall shortening than observed with aortic constriction by transient constriction of the left circumflex coronary artery. However, this intervention had no effect on right ventricular free wall segment work output. CONCLUSION: Increased left ventricular afterload decreases global and regional right ventricular stroke work at any given preload, a direct, negative systolic ventricular interaction.